Background: Tumours are not only composed of malignant cells but also consist of a stromal micro-environment, which has been shown to influence cancer cell behaviour. Because the ageing process induces accumulation of senescent cells in the body, this micro-environment is thought to be different in cancers occurring in old patients compared with younger patients. More specifically, senescence-related fibroblastic features, such as the senescence-associated secretory profile (SASP) and the induction of autophagy, are suspected to stimulate tumour growth and progression.
Methods: We compared gene expression profiles in stromal fields of breast carcinomas by performing laser capture microdissection of the cancer-associated stroma from eight old (aged ≥80 years at diagnosis) and nine young (aged <45 years at diagnosis) patients with triple-negative breast cancer. Gene expression data were obtained by microarray analysis (Affymetrix). Differential gene expression and gene set enrichment analysis (GSEA) were performed.
Results: Differential gene expression analysis showed changes reminiscent of increased growth, de-differentiation and migration in stromal samples of older versus younger patients. GSEA confirmed the presence of a SASP, as well as the presence of autophagy in the stroma of older patients.
Conclusions: We provide the first evidence in humans that older age at diagnosis is associated with a different stromal micro-environment in breast cancers. The SASP and the presence of autophagy appear to be important age-induced stromal features.
Keywords: Ageing; Autophagy; Breast cancer; Gene expression; Old patients; Senescence; Senescence-associated secretory profile; Stroma.